The New Test Images - A carefully chosen set of high-resolution
high-precision natural images suited for image compression research and
algorithm evaluation. The images historically used for compression
research (lena, barbra, pepper etc...) have outlived their useful life,
they are too
small, come from data sources too old and are available in only 8-bit
precision.

64-bit Entropy Coding - The limitations
faced by compression algorithms using arithmetic-coders and range-coders on 32-bit platforms and how
using 64-bit arithmetic can improve compression significantly.

64-bit Arithmetic Coding source - 64-bit arithmetic coder based on Mark
Nelson's code (which is based on CACM87 code). Read the above article for how it compares to the 32-bit version.

64-bit Range Coding source - 64-bit range coder based on Dmitry Subbotin's
carry-less implementation. Read the above article for how it compares to the 32-bit version.